Many efforts have been made in the past to classify and analyze cell structures that include viruses and other components. Various image analysis methods have been developed to describe, segment and classify viruses by using available image technologies. For example, cryo-electron microscopy has been used but the structures of the cells and the viral particles are not shown very well. It has also been difficult to objectively, repeatedly and reliably describe the cell components to accurately determine the maturity stages of the cell components.
More particularly, virus assembly is an intricate process and a subject of intensive research. Viruses utilize a host cell to produce their progeny viral particles by undergoing a complex process of maturation and intracellular transport. This process can be monitored at high magnification by utilizing electron microscopy (EM), which allows visual identification of different types of viral particles in different cellular compartments. Important issues that remain to be resolved include the identity of the viral proteins that are involved in each step of this virus assembly process as well as the mechanism of the underlying intracellular translocation and localization of different types of viral particles during virus maturation. Structural aspects of the virus maturation are generally hard to address although visualization techniques such as tomography and cryo EM have contributed to the available information on virus structures. These techniques may be used to provide information on stable mature viral particles. Genetic tools are available to produce mutants of key viral protein components. EM may be used to visualize the structural effects. However, there are no proper tools to characterize the structural effects, especially intermediate and obscure particle forms and to properly quantify them in an objective way.
This partly explains why the previous analysis methods have not been very effective and there is a need for more effective methods for analyzing cell and viral particle structures. There is a need for image analysis tools to characterize and quantify viral particle maturation and intracellular transport to facilitate objective studies of different virus assembly. There is also a need for an effective method for identifying and quantifying viral particles depicted in an image.